A new study by Fair Isaac, the creator of the FICO credit score, shows that 11% of U.S. consumers, about 22 million people, had their lines cut or accounts closed even though they pay their bills on time and have good credit. This is more than double the 5%, or 10 million consumers, who had blemished credit and saw their lines reduced in that same period, the six months ended last October.

As more lenders tighten up on credit, consumers can't afford to be complacent about their scores, Ulzheimer says. By the end of 2010, banks will slash $2.7 trillion of credit on cards, estimates bank analyst Meredith Whitney.

Fair Isaac says its analysis is ongoing. It plans to release additional findings in June.